You probably already know that Mass Effect 3’s galaxy-spanning PSN cooperative campaign pits two to four players against wave after wave of relentless Reaper forces. In this way, the basic premise of Mass Effect 3’s Galaxy at War co-op mode isn’t all that different from Call of Duty’s Nazi Zombies or Modern Warfare 2’s Spec Ops.

Players will be presented with a large, interactive map that will enable teams to hop into different theaters of war spread around the galaxy. You won’t be able to port your Commander Shepard into the co-op Galaxy at War mode (unfortunately); instead, you’ll create a new character from scratch, earning XP by slaying enemies and completing objectives. The co-op scenarios are heavily combat focused, though simple objectives — such uploading computer files or disarming bombs — creep in from time to time. The pace is fast-paced and grueling, and your goal is simple: outlast your Reaper attackers. To survive, teamwork and coordination with your teammates will be critical or you won’t survive.

The progression in Galaxy At War mode is wave-based and hierarchical, starting with squads of grim-faced Assault Troopers and eventually escalating into laser-rifle-toting Nemesis assassins and hulking Atlas mechs (and worse, presumably). As you lay waste to wave after wave of Reaper forces, you’ll accumulate weapons and assign new gun mods and skills before topping off at a level cap of 20 — just like in the single-player game.

In the heat of the Reaper onslaught, melee attacks, tech powers, and biotics are critical to your survival, so choosing co-op partners with complementary skills and equipment will be a key consideration. As an example, a well-timed Tech skill such as Incinerate or Overload can zap a shielded enemy, giving your teammate a moment to slink to safety and finish the job; a Biotic expert can Pull enemies out of cover to expose them to gunfire. As in any co-op game, communication will be key. One immediately helpful UI touch: you can easily spot your teammates through walls via ghostly outlines.

Single-player purists can stop worrying that this new mode wills somehow take away from the single player mode, it is designed to be a nice complement to that: Through this new mode you will have the chance to experiment with a plethora of character builds away from the stiff consequences of the single-player battlefield, and bust some Reaper heads with your friends. Playing the multiplayer mode will also unlock certain content in the single-player campaign, though exactly what that content is Bioware isn’t saying just yet.

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